Hi Everybody, I've just begun the basics of metabolism in my course and I need some help understanding the information I've learned.

I understand that the Kreb's Cycle (or Citric Acid Cycle as it's otherwise known) will produce acetyl. A single acetyl molecule used in one turn of the krebs cycle will produce:

3 NADH + H+
1 FADH2
2 GO2
1 GTP

These products will then enter the "next step" Oxidative Phosphorylation and the Electron Transport Chain, which uses the H+ ions from the products above with oxygen to produce water and ATP.

1st Question:

The thing I don't understand is are how are the oxidative and phosphorylation and electron transport chain different, is this just one step where the NADH H+ and FADH2 are oxidised and ATP formed or are they 2 different steps, and what happens in each different step (this might just be something I need to read more about)

2nd question:

Also are all the products of the krebs cycle used up completely in the Oxidative Phosphorylation and Electron Transport Chain step or are there other products left other than ATP and Water?

3rd Question:

Before anything can enter the krebs cycle, must it first go through a specific catabolic pathway i.e Glycolisis for glucose, fatty acids in beta oxidation?

These might be very basic questions for people on this forum but it's something thats confused me, I will keep reading but thanks to anybody who can help me with the questions above

1. oxidative phosphorilation has 2 steps: oxidation and phosphorilation.
oxidation: transport of electrons along the electron transport chain from NADH(or FADH) to O2. some of the energy is stored by pumping protons along the inner mitochondrial membrane, creating a proton gradient.
phosphorilation: the proton gradient is used in the process of making ATP. the enzyme functions just like a mill that uses protons instead of water.

2. the krebs cycle produces ATP, water, CO2, NADH and FADH2. NADH and FADH2 is used in oxidative phosohorilation.

3. some substances can enter the krebs cycle directly, if they are intermediates of the krebs cycle(malic acid, citric acid etc). however, this is done by the cell only to increase/decrease the number of intermediates, therefore as a regulatory mechanism. all the substances used for production of atp(glucose, fatty acids, glycerol, amino acids etc) go through other processes before they can enter

"As a biologist, I firmly believe that when you're dead, you're dead. Except for what you live behind in history. That's the only afterlife" - J. Craig Venter